At an oil refinery, crude oil is brought in, generally through a pipeline, at a temperature of approximately 50-70° F. Before the crude oil enters a crude heater, the crude is pre-heated to a desired temperature to optimize the performance of the crude heater and reduce fuel costs. Once the crude oil is pre-heated to a desired temperature of 350-400° F., it enters a flash drum or flash tower, wherein the lighter hydrocarbons (such as butane, propane and gasoline) are removed from the crude oil by evaporation or flashing. The remaining crude oil is then transferred to the crude heater for further heating prior to separation in the crude tower.
It is well known that fouling in the preheat circuit, progressively worsens as the crude temperature increases, cumulating with the most extensive fouling being observed in the crude heater. Fouling has also been observed in kerosene sections of the crude tower with excessive levels of phosphorus not normally expected nor historically observed in the foulants. Samples of the coke obtained from the pre-heat exchangers and crude heaters indicate these elevated levels of phosphorus. Phosphorus is known to reduce corrosion. Chemicals containing Phosphorous are understood to be utilized in the production or transportation of certain types of crude oils. It is believed that the elevated levels of phosphorus are contributing to the excessive fouling observed in the preheat exchanger circuits and crude heaters.